This invention relates to an electromagnetic relay usable as a high-capacity power relay and in particular to such a relay having contact points with an improved contact mechanism.
As shown in FIGS. 23–26, a prior art electromagnetic relay is comprised of an operating part 101 and a contact point block 102, the operating part 101 having an electromagnetic block 105 with a coil 105A and an iron member 106 contained inside a case 104 such that an attractive force is generated at the magnetic pole part 107 of the iron core as the coil 105A is excited and the iron member 106 is oscillated to the left around its supporting point 106A.
The contact point block 102 is formed with a base 108, a guide 109, a terminal table 110 and a returning spring 111. As shown in FIG. 25A, the terminal table 110 is provided with a guide containing part 118 and contact point containing parts 120, each contact point containing part 120 containing a fixed contact point 121. The guide 109 is separable into an upper main body 109A and a lower main body 109B, as shown in FIG. 24. The upper main body 109A has an upward protrusion 112 at its left-hand end, and the lower main body 109B has a downward protrusion 113 at its right-hand end. A spring container 112A is formed at the base of the upward protrusion 112, and the downward protrusion 113 is formed with an indentation for engagement (not shown).
Four insertion parts 114 are formed longitudinally along the upper guide main body 109A. As shown in FIG. 25A, a spring container 114A is formed at an end part of each of the insertion parts 114 and mobile contact points 116 are affixed to both end parts on the left-hand surface (on the side facing the fixed contact points 121) of a contact member 115.
The spring container 114A of each insertion part 114 contains a contact point spring 117 which contacts a corresponding one of the contact members 115 such that each contact member 115 is pressed to the left-hand wall part of the insertion part 114 by the biasing force of the contact point spring 117, as shown by broken lines in FIG. 25B. Both end parts of the contact member 115 are inside the corresponding one of the contact point containing parts 120 and the mobile contact points 116 are opposite the fixed contact points 121.
The guide 109 is contained inside the guide containing part 118 with its upward protrusion 112 inserted into an opening (not shown) formed in the ceiling part of the guide containing part 118 and its downward protrusion 113 inserted into an insertion opening 108A provided through the base 108. The guide 109 is normally at its returned position as shown in FIG. 25A by the biasing force of the returning spring 111.
The electromagnetic relay is formed with this contact point block 102 connected to the operating part 101. In this condition, a protrusion 106B at the top of the iron member 106 is oscillatingly engaged in the aforementioned indentation formed in the downward protrusion 113 from the lower guide main body 109B.
When the coil 105A of the electromagnetic block 105 is not in an excited condition, the guide 109 is in the aforementioned returned position by the biasing force of the returning spring 111. As the coil 105A of the electromagnetic block 105 is excited, an attractive force is generated to magnetic pole part 107 of the iron core and the iron member 106 is caused to oscillate to the left around its supporting point 106A such that the guild 109 is shifted against the biasing force of the returning spring 111 and the mobile contact points 116 are caused to contact the fixed contact points 121.
As another example of prior art electromagnetic relay, Japanese Patent Publication Koho 5-342964 described a structure comprising an electromagnet part, a contact point table, an insulating plate and a case. A base is formed with the contact point table and the insulating plate, a guide being slidably inserted into a groove formed at the center of the base. A fixed terminal of contact point terminals is set inside each of a plurality of chambers provided at fixed intervals opposite on both sides of this groove, and mobile contact points of contact members protruding sideways at equal intervals from both sides of the groove and being biased by means of springs are disposed opposite the fixed terminals. As the coil of the electromagnet part is excited and a mobile iron member is rotated, the guide is moved against the biasing force of a returning spring and the mobile contact points are pressed against the fixed contact points.
With both of these prior art electromagnetic relays, the contacting mechanism gains a pressure by means of the guide 109, the contact member 115 and the contact point spring 117. With such a mechanism as shown in FIG. 25B, it is necessary to increase the load on the contact point spring 117 to obtain a contact point pressure by limiting the separation of the mobile contact points 116 at the time of contact point contact (bouncing and chattering) and the rise in temperature by the passage of the current. For this purpose, since the characteristic of a relay is as schematically shown by the graph of FIG. 26, it is necessary to increase the attractive force of the coil from A to B and this means an increase in the consumption of electric power. In order to limit the increase in the power consumption by the coil 105A, however, the load on the contact point spring 117 must be limited and this can cause problems related to the separation of the contact member 115 due to vibrations and generation of heat.